A pseudo wire (PW) is a technology for providing, over a single packet switched network, line services such as the Ethernet (registered trademark) and asynchronous transfer mode (ATM), and is used for layer-2 virtual private network (L2VPN). Virtual private LAN service (VPLS) is a type of the L2VPN which realizes full mesh connections among a plurality of sites by use of the pseudo wire, as depicted in FIG. 22. A MPLS network is used for the VPLS, as a packet switched network. Referring to FIG. 22, reference alpha-numeral PE denotes a provider edge, reference alpha-numeral CE denotes a customer edge, and reference alpha-numeral FR denotes a frame relay.
With respect to the network technology mentioned above, Japanese Laid-open Patent Publication No. 2006-237678 discloses that an available bandwidth is allocated, by an egress node of a tunnel on which traffics are concentrated, to each of sessions to be multiplexed into the tunnel, and is then notified to an ingress node of the tunnel, which notifies the originating site of a packet to be transmitted, such as a home rooter or terminal device, about the available bandwidth.